The present invention relates to an information-recording medium which can make real-time recording of digital information such as an analogue signal, for example, an image or a sound which has been subjected to frequency modulation, data of electronic computers, a facsimile signal, a digital audio signal or the like by using recording energy beams such as laser beams and electron rays.
There are various principles of carrying out recording in thin films by laser beams and the like. Among them, the recording by changing of atomic arrangement such as phase-transition (also called phase change) of materials of the recording layer, diffusion of atoms between layers of a thin film or photo-darkening has the advantage that double-sided disks made by direct lamination of two disks can be realized because this recording involves substantially no deformation of the thin film. Many applications have been filed on the inventions relating to the recording of this kind. That is, with reference to the phase-transition of materials in the recording layer, Japanese Patent Kokai (Laid-Open) No.57-24039 discloses thin films of Sb.sub.25 Te.sub.12.5 Se.sub.62.5, Cd.sub.14 Te.sub.14 Se.sub.72, Bi.sub.2 Se.sub.3, Sb.sub.2 Se.sub.3, In.sub.20 Te.sub.20 Se.sub.60, Bi.sub.25 Te.sub.12.5 Se.sub.62.5, CuSe and Te.sub.33 Se.sub.67. Japanese Patent Kokai (Laid-Open) No.61-171389 and U.S. Pat. No. 4,866,672 make mention of Sn-Sb-Se thin films.
The above-mentioned information-recording media of prior art are not optimized in the composition of the recording layer and in the structure of the film. Therefore, when used as information-recording media of WORM type (namely, the type of write once, read many times) or rewritable type, they all suffer from the problems that they must be initialized before recording, they absorb less semiconductor laser beams and are inferior in recording sensitivity, they are not sufficient in intensity of read-out signal, they are great in distortion of read-out wave form and they are inferior in stability of amorphous state.